This essay examines some ethical aspects of stalking behavior in cyberspace. We have argued elsewhere that recent online stalking incidents raise a wide range of ethical concerns, including issues affecting gender (Grodzinsky and Tavani, 2001), personal privacy (Tavani and Grodzinsky, 2002), and physical vs. virtual harm (Grodzinsky and Tavani, 2002). The primary axis of discussion in this essay has to do with implications that cyberstalking has for our notion of moral responsibility, both at the collective (or group) and individual levels. For example, do collectivities and organizations such as Internet service providers (ISPs) have any moral obligations to cyberstalking victims, which go beyond legal obligations covered in strict liability law? And do ordinary Internet users have a moral obligation to inform (and possibly also to assist) persons whom they discover to be the targets of online stalkers? In our analysis of these questions, particular attention is paid to a cyberstalking incident involving Amy Boyer.